1. Field of the Invention
This invention relates to gas-fired fireplaces and other hearth products and provides a method and apparatus for achieving a yellow, aesthetically-pleasing and realistic flame which closely simulates a wood-burning flame, and which produces low carbon monoxide emissions.
2. Description of Prior Art
Gas fireplaces are becoming increasingly popular in both new home construction and in retrofitting wood-burning fireplaces in existing homes. Popularity of gas fireplaces over traditional wood-burning fireplaces is driven by several factors. Some states and localities have introduced legislation limiting wood-burning fireplaces because of the pollutants generated by burning wood. Wood can also be relatively expensive in some localities, and consumers often merely do not want the inconvenience of storing and transporting wood for a fireplace.
Traditionally, however, gas-fired fireplaces, for example those using natural gas or propane, have not been successful at simulating the appearance of a natural wood-burning flame. Because the velocity and flow rate of gas used in such gas-fired fireplaces remains relatively stable, flames generated by the gas also remain relatively stable and unchanging in appearance, unlike the flickering and rapidly changing flame associated with a wood-burning fire.
Attempts have been made to simulate the appearance of wood-burning fires with gas-fired burners.
U.S. Pat. No. 5,092,313 discloses a gas log fireplace which achieves a high heat output and highly efficient combustion. The fireplace includes a plurality of vertical gas ports and a fibbed heat exchanger positioned above a firebox which enhances heat transfer into the surrounding environment.
U.S. Pat. No. 4,886,445 teaches a gas burning artificial log assembly which includes a burner pan and a burner manifold which form adjustable elongated exit slots that are aligned parallel to artificial logs.
U.S. Pat. No. 4,838,240 discloses a gas burner assembly which includes a gas distribution tile having a plurality of vertical holes which form a honeycomb-like pattern.
U.S. Pat. No. 5,000,162 discloses a gas burner system having decorative gas logs. The burner system includes a plurality of nozzles for producing flames between the logs.
U.S. Pat. No. 4,883,043 discloses a gas-fired fireplace assembly having a plurality of nozzles positioned between artificial logs. The '043 patent indicates that the nozzles are capable of generating yellow flames which simulate a wood-burning fire.
U.S. Pat. No. 4,930,490 discloses a gas log apparatus which includes a ported chamber. The ports are rectangular, and are formed at the apex of a v-shaped ridge. The ports have sharply angled comers. The sharp vertices provide turbulence which the '490 patent indicates produces a ragged yellow and luminous flame.
U.S. Pat. No. 5,081,981 discloses a gas fireplace burner assembly which includes a burner tube that provides a plurality of separate yellow flames of different heights and widths between artificial logs of the assembly.
U.S. Pat. No. 5,320,520 discloses a gas burner assembly for simulating a wood-burning fire. The assembly includes two v-shaped grooves having a plurality of slots in the apex of the groove. Fuel is discharged through the slots and a flow of secondary air is directed into the flames to enhance flickering to simulate a wood-burning fire.
U.S. Pat. No. 5,139,011 discloses an unvented gas-fired heater assembly. A duct assembly directs heated air from the heater assembly into a room.
U.S. Pat. Nos. 4,971,031 and 3,382,861 disclose gas-fired burners which include a plurality of slotted ports through which a combustible gas flows.